A waste heat utilization device for an internal combustion engine is mounted on a motor vehicle, for example. This type of waste heat utilization device is provided with a Rankine cycle including a circulation path for circulating a refrigerant as a working fluid therethrough, and an evaporator for heating the refrigerant by means of waste heat of the engine of the vehicle, an expander for expanding the refrigerant delivered from the evaporator to produce driving force, a condenser for condensing the refrigerant delivered from the expander and a pump for pressurizing the refrigerant delivered from the condenser to be fed to the evaporator are successively inserted in the circulation path. The Rankine cycle recovers the waste heat from the engine.
A heat engine has been disclosed in which ethylene glycol is used as an intermediate medium for absorbing waste heat of the cylinder block of the engine as well as waste heat of the exhaust gas so that the heat absorbed by the ethylene glycol may be transferred to the refrigerant (see Patent Document 1, for example).
Also, a technique has been disclosed in which a cooling water circuit using Long Life Coolant (LLC) as engine cooling water is provided and an exhaust gas heat exchanger for transferring heat from the exhaust gas to the LLC is inserted in the circulation path of the cooling water circuit (see Patent Document 2, for example).